Telegraph system



Feb. 19, 1924; 1,484,386

G. C. CUMNHNGS TELEGRAPH SY STEM iled Dec. 20. 1919 4 Sheets-Sheet 1 All A n l lllll Al H I /nvenf0r rm/"7e C Cummings Airy Feb. 19, 1924. 1,484,386

\ s. c. CUMMINGS TELEGRAPH 5! STE M Filed Dec. 20. "$319 4 Sheets-Sheet 2 MIN hum-1P /h venfor: Gav/ye C Cummings y/M M 76 Feb. 19, 1924.

e. c. CUMMINGS TELEGRAPH SJSTEM 4 Sheets-Sheet 3 Filed Dec. 20. 1919 lmkenfor: 660/76 C Cum/77mg:

Feb. 19, 1924.

G c. CUMMINGS TELEGRAPH SYSTEM 4 Sheets-Sheet 4 Filed Dec. 20. 1919 Patented Feb. 19, 1924.

UNITED STATES PATENT OFFICE.

GEORGE C. CUMMINGS, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELEQTRIC COMPANY INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

Application filed December 20, 1919.

mitted over a line to which telephone apparatus is also connected.

The principal object of the invention is the provision of a telegraph system wherein means is provided for preventing telegraphic signals from interrupting or disturbing the operation of the telephonic apparatus which;

may be associated with a line over which telegraphic signals are also traversing.

A second object of the invention is' the provision of means, for suppressing disturbing harmonic frequencies created during the transmission of alternating current signals.

Another object of the invention, is to provide in conjunction'with a svstcm of the character as above referred to. means for preventing the absorption of the telegraphic signaling currents by the composite equipmeut connected with the line.

Another object of the invention, is to provide means for excluding from the alternating current telegraph apparatus currents other than those transmitted from the alternating current source.

A conversation carried on between two parties over a line over which telegraphic signals are being simultaneously transmitted has been found to be interfered with due to the presence of currents'dfa frequency con siderahlv higher than the fundamental frequency generated at the alternating current source. This causes considerable noise in the telephone circuit and therebymaterially impairs the cilicicncy of the system. But in the present system this ditliculty has been overcome by the introduction of suppression fillers between the alternating current source and the line. These filters have the inductance and capacitance values thereof so chosen as to suppress the currents of a frequeucy other than the fundamental fre- IELEGRAPH SYSTEM.

Serial 1T0. 846,370.

. quenoy of the generated current. It is thus evident that the characters transmitted from a telegraphic key connected in series with the alternating current source, as sent over the line, will not be distorted and at the same time, render the balancing of the line much easier.

In a system in which both alternating and direct current signals are transmitted, the direct current signals tend to affect the alternating current receiving device and thereby make it ditlicult to actually detect the alternating current signals. This, in the present invention, is overcome by means of the insertion of a filter in bridge of a coil of the transformer which connects the alternating current receiving circuit with the line. The inductance and capacitance values of this filter are so chosen as to filter out or suppress currents of a frequency other than those of the frequency as generated at the alternating current source.

As a means for suppressing the higher harmonics generated at the alternating current source" there is inserted between the source and the point of its connection with the line a filtering network which prevents the higher harmonics from being transmitted to the line and telephone apparatus assoeiatedthercwith. The alternating current receiving apparatus is rendered opaque to direct current signals by the provision of a filtering network connected in bridge of the circuit connecting the alternating current receiving apparatus with the line. In. preventing the alternating current signals from interfering with the direct current signals and the phantom circuit. there is interposed between these two parts and the point of their connection with the line, another filtering network for excluging currents of the frequency as generate at the alternating current'source.

It is thought that a more definite understandingof the invention may be had from the following description when considered in conjunction with the accompanying drawing. in which Fig. 1 shows a telephone line overwhich both direct and alternating current telegraphic signals are adapted to be superimposed. Fig. 2 shows another embodiment of the invention in which there is shown an alternative arrangement for 0011 necting the telephone branch or composite equipment with the line Fig. 3 shows another embodiment of the invention in which the alternating current receiving and transmitting means is inductively coupled with the telephone line. Fig. 4 shows the application of the invention to a grounded line; while Fig. 5 shows an alternative method of connecting the alternating current receiving means, as employed in Fig. l with the line Referring now to the drawing, paying particular attention to Fig. 1, in which there is shown two line conductors 4 and 5 which form a metallic telephone circuit and upon whu-h there is also adapted to be superimp sed both direct and alternatii'ig current telegraphic signals. A direct; current duplex equipment is connected with each of the conductors 4 and 5 only one of which is shown and are so arranged that it is possible to transmit direct current signals over both sides of the line. The line conductors termi natc in a bridge 90 to which is inductively coupled the telephone circuit and the altersatin; current receiving and transmitting circuits. Each of the direct currentduplexes is also connected with the line through a portion oi this bridge. (min-acted in bridge of the circuit conductors forming a part of the prcriiuisly referred to bridge are condensers 8, 5). ill and 11 and an induction coil 7 the midpoint of the inductiiin coil 7 being c nnected to ground for the purpose stated below. In shunt of the condensers 8 and 9 and the inductance 11 there is a second induction coil 6. At the middle point of the inductance 6 av lead is taken oif which serves as one side of the phantom circuit while the middle point of the coil 7 is grounded for the purpose of protecting the phantom circuit from serious transmission losses and since it is connected with the direct current duplexes thtough the condensers 12 and 13, it prevents mrious crossfire between the signals being transmitted over cachof the con ductors 4 and 5. t

The direct current duplex equipment is as shown, of the standard type and comprises a sending key 14 for connecting with the apex of the ratio arms 15 and 16 a source of potential the polarity thereof being adapted to be varied. In circuit with the key 14 and the apex of the ratio arms 15 and 16 there is connected an inductance 17 and a condenser 18 which serve to round off the direct current telegraph signals and is often times termed a noise killer. There is also provided the usual polarized relay 19 for controlling the operation of a receiving sounder such as 20 for enabling an operator to readily detect the signals as transmitted from a distant station.

An artificial line is connected with the ratio arms and i for the purpose as is well known to balance the line for taking care of disturbances and other causes which tend to distort and interfere with signals transmitted over the line. An inductance 74 is inserted in 'series with the line and direct current duplex equipment. which when taken with the condenser 12 tends to more completely round oil the direct current signals. Since he direct current duplex arrangement does not form a part of the present invention and since the method of operation thereofs well known to those skilled in the art, a-dctailed description of this part of the system has been omitted.

As to the alternating current signals, a, generator 21 for generating a current of approximately 80 oycles is employed in circuit with which is a transmitting key 22. This key is for the purpose of connecting the source of alternating current to the primary coil of a transformer 23 through which the current is transformed to the secondary coil thereof and then to the primary coil of a transformer 24. A set of inductive resistances and condensers such as 25 and 26 is interposedbetween these two transformers and malte up what is known as an electric filter. The resistances are connected in series with the two coils of the transformer-s23 and 24 respectively. while the condensers are connected in bridge thereof. In the genera; tion of alternating current. a certain fundamental frcquency is generated but in the transmission of telegraphic signals by means of a key. it is impossible'to depress the key at the instant. the generated current is zero which thereby produces harmonics of a magnitude and frequency considerably higher than the fundamental. The opening and closing of the circuit by means of the key 12 thereby produces what is termed transient currents which are very noticeable in the telephone circuit if the key is depressed when the current is of a value other than zero. These transient. currents tend to produce in the telephone circuit suitablvconnected with the line disturbances which'are very disagreeable to parties carrying on a conversation. The introduction of filters as before described thus tends to suppress these transients whereby the frequency of the current as actually transmitted to the line is of a uniform value, and there will not be present the higher harmonics which would be present if such were not provided. These transient currents also tend to unbalance the line and thereby render it dillicult to accurately balance the same to take care of various changes in line condition.

The secondary coil oflhe transformer 24 is in a loop or network 52 which is somewhat similar to a lVheatstone bridge and com prises a coil of each of tho transformers 24- 27 and 29 respectively. To that portion of transformer 27 which is in the bridge circuit 52 ther is connected the u ual artificial hal ancing network, and in order to simplify the circuit arrangement it has heen omitted. hut is however. represented hr the ret angle 2.). The mid point of one of the coiis of the transformer 27 is grounded through a retardation coil 3!) for preventing the crossfire of the direct current duplexes operating upon each of the wires -1 and 5 and also in creases the transmission elliciencv of the telcphone circuit. There is connected across the zero potential points of this hridge. as viewed from the alternating current tele graphic transmission voltage standpoint, two circuit arrangements. one of which serves as a means tor receiving the alternat ing current telegraphic signals while the other is for the purpose of receiving: and transmitting currents from such telephone apparatus as may he associated or connected therewith. In the telephone side whi h is to the right of the dotted line 2.? there is connected in each of the condiu-lors ill and 32 a resonant unit consisting of condensers 33 and 34 and iuductances 35 and 36 respectively. There is also connected in bridge oi these conductors. a unitcoiu]u.'isin an iudiu-tanre ii. and a condenser 38. These units have their in ductan cs and capacitance so computed as to suppress or exclude telegraphic signals and likewise to prevent them from heing unduly ahsorhed by the composite or telephonic equipment associated with the line conductors. repeating: coil 39 has one coil in circuit; ivith these units while the oth r coil thereof is onuertcd with the condn tors 4t) and 41. These conductors are su itahly connected with the usual telephone equipment and since this does not form a part of the present invention and is well known, it as been omitted from the drawing in order not to complicate the circuit arrangement.

he receiving means for the reception of the alternatin; current signals. as shown to the left of the dotted line 2-? is coupled to the network hv means of a repeat in coil l9v A \virnlin; of this repeating coil also forms a part of the network or loop circuit in which is connected in liridge a unit comprising an indiu-tance H and a condenser it to ,qcther with a vzu'iahie' resistance element 4:"). The resistan e element 45 serve to \':ll the strength of the incoming f' lfllltllfi and \vhir'h is techni ally termed ain' This. there fore. provides for variations in the length ot the line over which the signals are being: transmitted. The unit consi liu; oi the ill-- (luv-lance l-l and the cornlonscr i the values of whi h have been computed art for the purpose of suppressing any extmncous cur Itllts which may have heen superimposed on the line conductor as well as rendering it sulistflut iall v opaque to dircct' current signals. Thc in' luctance 1 is of a low value such as approximateh l henrv while the condenser 4-1 is of a comparatively high value and the two when taken togethertherefore have a very low impedance value to currents of a frequency other than those generated at the alternating current source. while it readily allows currents of a frequency the same as that generated at the altcrnatimg current source to pass through to the alternating current: receiving circuit. A loose coupling 16 is also suitahly connected with the loop circuit mentioned above and connects the sainc u ith the various thermionic amplifiers for amplitvin; the signal waves. This loose coupling has two important functions. one heing to increase the selectivity of the receiving circuit and the other to further renrler the circuit opaque to direct current 'signals.

circuit is made up of a numher of vacuum tnhcs or amplifiers such as IT. 48 which serve to amplify the received al ernating: currents, while the tuhes 49 and 5t] are for the purpose of converting the alternating current into pulsating and direct current impulses. The thermionic amplifier as herein empl ved is well lmmvn the art and a detailed description thereof is considered uunecessal ln There is associated with the output of these stone polarized relay 51. The enu'iloyment of a relay of this character permits of a considerahle amount of variation in the amplitude ol the lt'CllflPtl alternating: current signal without producing in the local sounder or other receiving circuit an undue amount ol distortion. A snitahle sounder to those skilled in amplifiers a \Vheat- The alternating current signal receiving such as tilt is connecteil with the vibrating arniat are of the polarized relay 51 and Serves as a means whereby an operator can detect the signals as transmitted from a distant. station. i

The network is coupled with tho line conductors! and 5 through the winding of a repeater coil 29. The middl point of one windin; thereof is rroun'dcd through a retardati n coil 53 for prcventin; cross fire ot the direct current duplcv equipments opcrating! on each side of the line coudilctors and also protects the phantom circuit from serious transmission losses. A pair of condeusers such a 51 and 55' are connected in the line condiutors l and 5 respectively and serve to impede the (lowing of direct. ourrent signals through the repeating coil 52 The nnit- 5 and :3? are connci ted in the circuit lietvvoon the rcpealiu coil Zw and the lu'idgc to which the phantom circuit is con nected. each comprisirn an inductance. and a condenser tor the purpose of preventing the alternating telegraphcarrier currents from interlcrin'r with the workings of the phantom circuit. It is thus seen that the currents as sup rimposed on the line conductors through the actuation of the key 4 menace 22 are prevented from being unduly ahrent. The resistance 45 is ad'usted to nib sorbed by the telephone equi ment which press on the thermionic ampliiier a current may be suitably connected wit the line. of a strength dependent upon the length of In a system of this caracter various the line extending between the two stations.

I methods of signaling may a carried on si The negative an sitive portions of the multaneously without dan r of interfering wave as transmitte passes through the rewith the other signals w ich at the same spective thermionic amplifiers where they time may be transmitted over the line. The are amplified and'rectified,and then throng efficiency of each of the several channels of the polarized relay 51 which controls 7 communication is in itself materially iuthrough its cohtacts the operation of the 1'6 creased and at the same time the maintainreceiving sounder 60. The receivingsounder once is necessarily decreased. 60 will thereby be'operated in accordance The operation of the system as hereinbewith the incoming signals. The alternating fore set forth is as follows: Let us assume current telegra hic signals are prevented 5 that both telegraphic carrier currents and from being un uly absorbed by the cein- 8 telephone currents are being nietallically posits equipment or the telephone branch transmitted over the conductors 4 and 5, 1; means of the filters connected in this the telegraphic signals being 'formed by branch as heretofore set forth. means 0 the transmitting key 22 in circuit In Fig. 2 there is shown the same arrange with the generator 21. These signals will ment as that of Fig. 1 with the exception 85 be repeate to the transformer or repeating of the method or manner of connecting the coil 23 passing through the inductances or telephone branch with the line conductors resistances 25 apd the condensers '26 to the 4 and 5. In this case the telephone branch transformer 24. Since the transformer 24 of the composite equipment is connected with 2 forms a part of the network 52-.11'l which the line conductors through the re ating 9 there is connected a transformer or repeatcoil 61 to which the one side of the p autom 'ing coil 28, the alternating current telegraph circuit as 62 is taken 05. The units 56 and signals thereby pass to the line conductors 57 thereby serve to suppress or exclude the 4 and fiiconnecting a distant station. It is, alternating current telegraph signals and of course, understood that the apparatus at prevents the same from interfering with the 06 the distant station is identical with that as transmission of telephonic currents.

The operation of the system is identical The placing of any bridge across the telewith that as described in connection with phone circuit increases thecrossfire inter- Fig. 1, and a descri tion thereof has been 85 ference between the direct current'channels. dis ensed with for t is reason. 10 To prevent this it is necessary to place a eferring now to Fig. 3 and the embodiground at the middle point of one oi-the ment illustrated therein, the method of concoils of transformer 28. Since a simple necting the telephone branch with the line ground at this oint would operate as a conductors is the same as that of Fi 2 40 short circuit. to t e phantom telephone cirand the dill'erenee lies in the method of cuit the inductance coil 53 is placed in this connecting the alternating current receivground ath and actsas a high impedance ing and transmitting circuit with the line. to the p antom telephone currents. In this case, they are inductively coupled Since the telephone and alternating eurwhile it may be noted in' the revious case rent signaling receiving circuit are conncctthey were directly connected with what was ed to the zero potential points of the nettermed a bridged network or a Wheatstone work 52 as viewed from the alternating curbridge. The arm ment shown in this rent telegraph transmitting voltage standfigure continues to imit the effect of the point, the working (it these cirgiiiits will not alternating telegraph currents in the telehe interfered with by currents emitted from' phone branches not' by connecting this 11 the alternating current soueceat the station hranch at points arranged to be at zero which is transmitting. The signals as transpotential with respect to the alternating mitted from the transmitting set or a discurrent transmitting voltage, but by relying taut station pass over the conductors 4 and wholly upon the use of filters in the line 55 5 in series and through the repeating coil circuit for aooom lishin this result. This 28 to the receiving circuit designed for this method is also em loye in the system as purpose. These signals pass through the shown in Fig. 2.; y rovulmg the filters inductance 58 which is tuned with the con- 56 and 57 composed Q suitable inductance denser 59 so as to be resonant to the ulterand capacitance, the potential of the alternating telegraphic current frequency and noting current source 21 need not he of as through the repeating coil 42 to the loose high a value as Jould be necessary if these coupling 46. The signaling current how units were omitted. This is due to the fact v ever passes through the filter as made up of that the absorption of the alternating our the inductance 43 and condenser 44 for the rent signals by'the composite equipment purpose of suppressing any extraneous curwould be such an to require a higher potens tial to produce the same character of impulses on the line conductors 4 and 5, on account of the distort ion which the signals will of coursc sull'cr. It thus licconlcs unncccssury to apply impulscs of a highcr potential to orcrcomc the cll'cct' of such absorption. ()briously. then. thc signals ie ccii'ed at tho distant cud of the linc condom tors 4 and 5 would not bc ol' the saznc wan: form if thc tiltcrs M5 and in" wcrc Hui ntilizcd for preventing the ululuc absorption of thc altcrnaling cnrrcnt signals by tho mimpnsitc iuipmcut. Thcsc units not only accomplish this rcsnlt. but also rcnilcl' thc dircct currcnt tclcgraph channel more cllicicnt and positive in llPll'iltlOll. 7

Tim alternating currcnt signals are lormcd in thc samc manncr as hcl'ore dcscrihcd andairc imprcwcd upon thc lint thrimgh-thc rcpcatiug coil 63. onc coil of which is groundcil at its middle point for the purpose ofequally dividing the currents between the two conductors. as wellas limiting the client of thc crossfire of the direct current duplexes opcrating on the line conductors 4 undo respectively. The network 29 which is for tho purposiof balancing the line. in Connection with inductanccs 64 and 67, and the condcnscrs 70 and 71 serve to balance the unit comprising the inductanccs 65 and 68, and thc condonsers 54 and 55 when considered with the line. These units. thci'clorc. whcnitaluai together render the primary windings of the repeating' coils 66 and 69 neutral with respect to the secondary windings thcrcof. In this way no potential is applicd lo the secondary windings of the rcpcating coils 66 and 69. and the receiving circuit is thcrcby unaffected by the transmission of altcrnating current signals.-

ncoming alternating current telegraph signals therefore pass through the repeat ing coils 66 and 6.) in the bridge conncctcd with the line conductors In bridge with the rccciving circuit; there is shown the inductance 4-3, condenser 14 and the variable resistance element 45 as hcfore mentioned. This shunt is of extremely low impedance to currcnts of any frcqucncy except, that, to which it is resonant and therefore serves to almostcomplctcly cxcludc from the alternating currcnt rccciving circuitinter lcrcnca currents doc to thc operation of the direct; current duplcx cquipmcuts on each of the line conductors. The rcmaindcr of the operation hf the systcln is the sam as that; previously dcscrihcd.

It. is oftcn vcry desirous: to hc able to secure an additional duplex channel over a singlc line being opcratcd citbcr direct current duplex or simplex An arrangemenl; of this charactcr is .iliown in Figs. 4 and 5 and will now be dcscrihcd. A line conductor such as 79 cxtcnds hctwccn two distant stations and terminates at eaeh of the stations in the circuit arrangement as shown in Figs. 4 and 5. The direct current duplex cquipnient is the same as that preiously dcscrihcd and is connected with the conductor 72 through an inductance '75. one terminal of which is grounded through a. condenser To. Thesc two when taken togcthcr scrvc to round off the pcaks of the waves as transmitted from the direct ourrcut duplcx cquipmcnt as well known in the art A second iuductanccTT is also couucctcd in the line and has a condenser 78 in bridge thcrcol, the purpose of which will bc moi-c clearly understood from thrrdcscription which is to follow. The alternating current transmitting circuit is inductively coupled with the line through a transformcr Til. one of the terminals of thc scc onilary coil thereof bcing gronndcd. There is al o connected in thc liuc various inductani-cs and resistances H". R]. 8; and 3 rcspcctivclu and thc condcuscrs bl of which are conncctcdin scrics with thclinc. and thc artificial balancing not work as at 86. 'lhc altcrnatiug current rccciving circuit is conncctcd across the tcrminals oi the indnctau cs Rt) and R3 and is arrangcd as \vcrc the other circuits prcriously dcscrilicd with an imluctaucc l3. condcnscl' ll auda \'ariable rcsistancc clculcnt 15 which scrvc the samc pnrposc as lict'orc. Thc transi'ormcr 42 couples lhc line with the rccciving polariiicd rclay .31 through suitablc amplitha-s in the samc nianncr as previously poiutcd out.- The rcmaining part of the rccciving circuit is identical with that as previously dcscribcd. i i i A tclcplione branch such as 87 is couplcd with tho line through a l'cpcuting (oil 88 having a lcrmiual at one of the windings thcrco'f"groundcd inasmuch as a single conductor is cn|plo \'cd. 'lhc rcpcating coil 88 is conncctcd with the linc through suitable inductanccs and eondcnscrs. In order to prorcul tlic flow of altcrnating tclcgl'a ll Signals through the telephone branch, tie inductance i? and condenser 78 have been inscrtcd in the line.

The arrangcincnt as shown in Fig. 5 is the same as that of Fig. 4 with the cxception of the nacthod of connecting the alternatin currcnt tclcgraph rccciving circuit with the line. In tho lattcr figure the rcccivmg circuit is lircctly connccted with the line While in the former it is inductivcly connected. The operation of the two systems is identical and a dctailcd description thereof is thought to be unnecessary.

What is claimed is:

1; In a telegraph system, a metallic line circuit connecting two stations, means for simultaneously transmitting both direct and altcrnating current: telegraph signals over said line circuit, a composite act connected and R5 all I lit intent connected to said com to said line circuit, telephone equipment associatcd with said com osite set, and means comprising a set of ters for preventing the su rimposing of said alternating current signals oncurrents in said composite set.

2. In a, t regraph system, a metallic line circuit, a source of alternating current of a predetermined freqncnc means for transmitting telegraph signs s over said line circuit from said source, a composite set associated with said line circuit comprising in ductance and capacitance, telephone equip site set, and parallel resonant units serial y connected in said line circuit for preventing the absorption of current rem said source by said conipcsite set.

3. In a telegraph"system comprising a line conductor, a source of alternating current, means for transmitting telegraph signals from said source, means for receiving such signals, a said receiving 'means with said line, an

means consisting or an inductance shunted hyja condenser connected in bridge of a winding of sa d transformer for excluding frdtn sav 'd receiving means extraneous curiIn a telegraph system, a line conductor, a urce of alternating current, a key for transmitting telegraph signals from said source, means for receiving such signals, an inductive coupling between said receiving means and said line, and means comprising an inductance and a condenser of comparatively low and high value respectively, con nected in bridge of said inductive coupling for excluding from said receiving means transformer for couplin signals transmitted from a source other than that of said alternating current source.

In a signaling system of composite'telcpliony and telegraphy, a metallic line circuit joining two stations, :1 source of alternating current of a frequency of approximately 80 cycles, means for transmitting telegraph signals from such source, com

osite set, telephone apparatus associated with said set, and an anti-resonant circuit interposcd between said alternating current source and said composite set for preventing the absorption of said 80 cycle current by said coinposite set.

6. In a Si sling: system of composite telephony an telcgra phy, a metallic line circuit joining two stations, a source of aiiermating currcntof a frequency of approximately 80 cycle! means for transmitting telegraph signals from such source a coznposite set, telephone apparatus associated with said set, and a parallel resonant unit associated with said composite set or preventing the absorption of said alternating current signals by said composite set.

7. In a telegraph system, a line, a source of alternatin current, means for transmit ting telegrap ic signals from said source, an induction coil inductively connecting said source of current with said line, and means interposed in the line between said induction coil and said source of current and effective due to the t ansmision of tele- ;rraphie signals for suppressing disturbing harmonic frequencies.

In witness whereof, I hereunto subscribe my name this 16th day of December A. D.,

GEORGE C. CUMMINGS. 

